OBDII INC Reading Question

I have a 2000 Jeep Grand Cherokee Laredo. It has not been driven for the past month. When I went to start it the battery was dead. Charged it and all running ok. I took it to the shop and had to have my Radiator Fan assembly changed as the fan was not working and the car would overheat if standing still and left running. After that I asked for an inspection. They told me it passed safety but the OBD had a problem. The results of the scan were Catalyst Mon-Inc, Evap System Mon-Inc, and Oxygen Sensor Htr Mon-Inc. The car seems to be running fine and it is not throwing any codes. I currently have an OBDII scanner and I confirmed the above with the addition of Oxygen Sensor Mon-Inc. I understand this means an Incomplete reading. Could it be because the vehicle was sitting for a while with a dead battery and I need to drive it for awhile?? Any ideas how long I will have to drive it?? I got a 10-day temporary inspection extension from NYS. Any help would be greatly appreciated.

It’s because the battery went dead. The monitors will complete after you drive it for a while, as long as you don’t disconnect the battery. The EVAP monitor usually does best with 3/4 tank of gas (no more). I don’t know how long it will take. There is a particular driving procedure that you can follow to speed things up, but I don’t have it.

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2 or 3 days of normal mixed driving, some highway, some city, should collect enough data. You can confirm that with your OBD-II scanner after a few days. I’ve had a few complete after a single day of regular commuting.

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As of today the Catalyst Monitor reads “OK”. The other two that are still reading “INC” are the Evap System Monitor and the Oxygen Sens HTR Mon…I just started driving it again yesterday 70 miles to work and 70 miles back pretty much all highway…Does anyone know or have alink to what the driving cycle should be for a 2000 Jeep Grand Cherokee Laredo?

I have the GM drive cycle and I’m betting if you follow that, you will cover the Jeep drive cycle. See below

General Motors Driving Cycle
A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:

Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50?C (122?F) and within 6?C (11?F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.

Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge “No Flow”, Misfire and if closed loop is achieved, Fuel Trim.

Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.

Decelerate. This will perform the same diagnostics as in step 5. Again, don’t press the clutch or brakes or shift gears.
Reprinted on OBDII web site courtesy of General Motors Corporation
? General Motors Corporation

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I don’t think the oxygen sensor heater monitor WILL complete. There is, probably, something wrong. The heater circuit needs to be checked out.

Why exactly would you say that? What are you basing this on?

The monitors need MIXED driving to complete. Some highway, some stop-n-go city. You’ll need to vary the driving a bit to get the monitors the data it needs.

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Thanks to everyone, last night after my commute to work all monitors registered ok. I got my car inspected this morning with no problems. Thanks for all your input.

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Hello all I have a 2005 Chevy Malibu classic and I’m having the same problem as the Jeep except for my car won’t actually start but it not showing any codes and it has catalyst mon- INC,EVAP system mon- INC, oxygen sens mon- INC, and oxygen system htr- INC. It did the same thing at the beginning of the year and got the fuel pump replaced and oil changed and about 2 months later is was down again, made it home park and got ready to go to the store later and it wouldn’t crank. It’s been down for almost 2 months now. I would greatly appreciate any advice.

Did you check the battery? What happens when you attempt to start it, anything at all? Can you hear the starter clicking?

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@kurtwm1 I charged the battery in order to put the obd 2 reader on it, once I charged the battery I turned the key over and it almost started but didn’t complete, I didn’t pay any attention to a sound.

Well, I have a feeling your battery is on its last legs. Even after charging, it may be sufficiently good to power your reader or some accessories, but probably not enough to turn the starter over. Have it checked at your local auto parts place. They do it for free.

@kurtwm1, ok thank you.